Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $54.94   13.157%   $62.1685   $62.17   $62.15   $62.20  
  Purchase #2 $169.78   8.612%   $184.4015   $184.40   $184.40   $184.40  
  Purchase #3 $32.79   10.380%   $36.1936   $36.19   $36.20   $36.20  
  Purchase #4 $109.52   8.302%   $118.6124   $118.61   $118.60   $118.60  
  Purchase #5 $112.59   10.304%   $124.1913   $124.19   $124.20   $124.20  
  Purchase #6 $131.47   13.525%   $149.2513   $149.25   $149.25   $149.30  
  Purchase #7 $228.98   5.656%   $241.9311   $241.93   $241.95   $241.90  
  7 purchase totals = $840.07       $916.7497   $916.74   $916.75   $916.80